I usually workout at night, and did a morning workout the other day due to schedule conflicts. I was doing a tape that I consider easy, and I could barely get through it!! I was so TIRED! It wasn't that I hadn't woken up, but that I hadn't eaten anything or had enough water yet. I think I was underfueled + dehydrated, which left me feeling drained towards the end of the workout. Perhaps you need a light snack, like a piece of fruit, and some extra water before your workout?
Also, I would recommend doing the cardio
before weight training. By the time you get to cardio, your muscles are fatigued from the weight training and not happy to be doing the extra work! Plus, your weight training will be more beneficial if your muscles are warmed up first.
Finally, one more suggestion -- perhaps you're simply bored! When I don't like my workouts anymore and feel like they're really a chore, the mere thought of working out makes me tired -- and makes it hard for me to get through a workout! Maybe it's time to mix it up a little! Try a new class, or do an outside activity a few days a week!
Hope any of this helps!